With the rapid development of display technology, touch screen panels have become popular in life gradually. At present, touch screens can be classified into the following types according to their operation principles: resistive type, capacitive type, infrared type, surface acoustic wave type, electromagnetic type, vibrating wave induction type, etc.
Capacitive touch screens have received much attention in the industry due to their unique touch principle and advantages such as high sensitivity, long life, and high light transmittance. Presently, capacitive touch screens are generally of a front-attachment type, in which capacitive touch driving electrodes and capacitive touch sensing electrodes both made of a transparent conducting material and insulated from each other are disposed. When a finger touches the touch screen, since the human body is a conductor, coupling capacitance is generated between the finger and both the capacitive touch driving electrodes and the capacitive touch sensing electrodes in the touch screen, resulting in capacitance variation around the touch point, which causes an induced current flowing through the touch point in the capacitive touch driving electrodes and the capacitive touch sensing electrodes. The position of touch point can be calculated accurately by relevant calculations.
Electromagnetic touch screens are widely used in many advanced computer aided design (CAD) systems such as AutoCAD due to its feature of realizing hand writing like original chirography. At present, electromagnetic touch screens generally adopt an electromagnetic antenna panel of a back-attachment type that comprises metal wires crossing each other horizontally and vertically. FIG. 1 is a structure diagram of an electromagnetic touch antenna panel in which metal wires in X direction and metal wires in Y direction are perpendicular to each other and insulated from each other by an insulating layer interposed therebetween. FIG. 2 shows the electromagnetism touch schematic diagram. Two metal wires, namely touch electrodes Y1 and Y2, are connected by a touch electrode in X direction to be equivalent to a resistance Rx. When an electromagnetic pen approaches the assembly surface and slides thereon, the electromagnetic wave passes through the wires, generating an induced electromotive force V, and the closer to the position of the electromagnetic pen, the stronger the induced electromotive force is. The magnitude of potential vector received by the touch electrodes Y1 and Y2 is equivalently expressed by the position of a sliding arrowhead over the resistor to thereby determine the magnitude of induced electromotive force on the electrode in Y direction, and ultimately determine the position in Y direction. In a similar way, the electrodes in X direction work in a same principle. Because these two groups of electrodes overlap each other, the movement of pen can be considered as synchronized sliding in a same direction or an opposite direction on two sliding resistors. Once the X and Y coordinates are determined, it is possible to calculate the coordinate position of the pen point on a plane. Meanwhile, the front end of the electromagnetic pen is provided with a pressure sensing device that can determine the wideness of chirography through the force of pressing, which is why the electromagnetic touch antenna panel can realize hand writing like original chirography. The main control chip processes and computes the voltage signals received by the touch antenna panel to obtain the position of the electromagnetic pen and the pressure of the pen.
At present, in order to realize dual touch by finger and pen, capacitive and electromagnetic types may be combined.